The present invention relates to a new and improved method for forming a pattern which includes a core which is at least partially covered by wax.
Articles, such as an airfoil, have been formed by a lost wax investment casting process. The process may include forming a pattern having the configuration of a space or cavity to be formed in a mold in which an article is to be cast. A core portion of the pattern has a configuration corresponding to the configuration of a space to be formed in the article.
To form the pattern, the core is positioned in a die cavity. Wax is injected into the die cavity around the core. The resulting pattern may subsequently be covered with a ceramic mold material.
Once the pattern has been covered with a ceramic mold material, the wax portion of the pattern is melted. The wax is removed from the mold to leave a cavity into which metal is cast. The core is at least partially enclosed by this cast metal. The core is subsequently removed to form space in the cast metal article. The space formed by the core may be a complex arrangement of passages.
The concept of supporting a core in a die cavity using fixed and/or spring loaded pins to support the core is disclosed in U.S. Pat. No. 4,283,835. A system which allows for design changes, such as a shift in core location, is disclosed in U.S. Pat. No. 7,296,615.